1. Field of the Invention
The present invention relates to a spark ignition engine, and more particularly to a controller used in the engine for ignition control and an ignition coil for use in the engine.
2. Description of the Related Art
In a spark ignition engine, it is known to perform spark ignition plural times for the purpose of improving ignitability and combustion stability. For example, JP-A-9-112398 (Patent Document 1) discloses a technique of performing spark ignition plural times during a compression stroke in an engine, which is provided with one spark plug and one ignition coil per cylinder, in order to prevent deterioration of the combustion stability when the ignition timing is advanced for some reason.
Also, JP-A-2002-206473 (Patent Document 2) discloses a technique of providing two ignition coils per cylinder and increasing the degree of freedom in setting the ignition interval in order to prevent a chance of firing from being lost during a non-discharge period that is generated when the spark ignition is performed plural times.